Download Maxillary second molar protraction with mini-implants

Case Report
By Neal D. Kravitz, DMD, MS
W
hen you are protracting maxillary molars,
often anterior dental anchorage or Class III
directional elastics are sufficient to consolidate
space without affecting incisor position. However, in more
challenging cases such as movement through a pneumatized sinus or molar substitution, skeletal anchorage may
facilitate efficient molar protraction. This case report
presents the treatment of an adolescent patient with early
loss of dysplastic maxillary first
molars and successful, noncompliant protraction of the second
molars using orthodontic miniimplants for anchorage.
molars, presence of all third molars, and acceptable condylar
head shape bilaterally (Figure 3).
Study model analysis revealed a Class II division 1 subdivision right malocclusion, a tapered-maxillary arch, 40% overbite, +4 mm of overjet, and moderate anterior crowding.
Treatment Objectives
Diagnosis and Etiology
A 13-year-old adolescent
female was referred by her general dentist for an orthodontic consultation following the
recent extraction of severely
carious maxillary first molars.
The patient presented with a
straight soft-tissue profile and
good facial symmetry, with the
maxillary dental midline left
of the facial midline. Intraoral
examination revealed missing maxillary first molars, full
eruption of the maxillary second molars, 180º malrotation of
the maxillary left second premolar, forward position of the
maxillary right buccal segment
due to the labially displaced
maxillary right canine, forward
position of the left mandibular
buccal segment due to lingually
displaced mandibular left lateral incisor, and coinciding dental
midlines (Figure 1).
As shown in Figure 2, cephalometric analysis confirmed
a mild Class II skeletal relationship (SNA: 79º; SNB: 76º). A
pretreatment panorex provided
by her general dentist revealed
large carious lesions with pulpal
involvement of the maxillary first
Maxillary second
molar protraction with
mini-implants and a
transpalatal arch
We identified five treatment objectives:
1)establish functional Class I
molar and canine occlusion
with normal overbite and
overjet;
2)resolve crowding;
3)develop a broader maxillary-arch shape;
4)align the dental midlines
with the facial midline; and
5) maintain soft-tissue esthetics.
Treatment Alternatives
Figure 1: Pretreatment composite.
Figure 2: Pretreatment cephalograph.
Figure 3: Pretreatment panorex provide by general dentist.
Notice the dysplastic first molars (yellow circles).
18 OrthodonticProductsOnline.com February 2011
The patient presented to
our office with the maxillary
first molars already extracted.
Therefore, our treatment options were limited to either
holding first-molar spaces for
restorative treatment or molar
substitution (protracting the
second molar into the first molar position). The maxillary left
second premolar would not be
derotated to avoid prolonging
treatment duration and risking
pulpal necrosis.
In regard to the first treatment option, the maxillary left
second premolar would benefit
from cuspal coverage; however,
no other posterior teeth had carious lesions. Therefore, we did
not want to prepare bridgework
on healthy teeth. Furthermore,
the patient was approximately 4
years from skeletal maturity, and
she was not interested in pursuing endosseous dental implants.
The second treatment option included protraction of the
maxillary second molars into the first molar position. To aid molar protraction, we discussed incorporating orthodontic mini-implants into the palate. Due to the cost savings and the preservation of
healthy teeth, this treatment option was chosen by
the patient and supported by her referring dentist.
Treatment Progress
We fitted all teeth, excluding the maxillary
first premolars, with fixed, preadjusted edgewise
appliances (Rocky Mountain Orthodontics Synergy .018 slot in the anterior and Synergy-R .022
self-ligating slot in the posterior. We ligated .014
NiTi aligning archwires (also from RMO). At
2 months of treatment, we switched to .016 x .022
NiTi archwires for anterior torque and arch development (Figure 4).
We placed two RMO Dual-Top mini-implants
(6-mm length and 1.6-mm diameter) in the paramedian region of the maxillary palate, in line with
the first premolars. We fitted bands on the maxillary first premolars for a pick-up impression to
fabricate an AOA Laboratories transpalatal arch
spanning premolar-to-premolar. I instructed the
laboratory technician to keep the buccal brackets and solder palatal buttons on the bands. After
fabrication, we cemented the transpalatal arch
with GC Fuji LC, and we added RM Bond flowable composite to secure the mini-implants to the
transpalatal bar (Figure 5).
After 4 months of treatment, we inserted .017
x 0.025 stainless steel archwires to begin consolidation. We placed buccal and palatal elastic chains
(RMO Medium-Energy Chain) for efficient molar
protraction. In less than 5 months (December 2007
to April 2008), we achieved complete space closure
with minimal crown tipping.
After 9 months of treatment, we removed the
transpalatal arch and mini-implants, then bracketed
the maxillary first premolars. We then performed
final arch coordination and minimal occlusal equilibration. Once panoramic evidence confirmed mesial
migration of the maxillary third molars into the second molar region, we bonded lingual retainers and
took impressions for overlay Hawley retainers. At the
debonding appointment, we gave the patient a referral for extraction of the mandibular third molars. The
total length of treatment was 16 months.
Figure 4: Treatment Montage. A) Upper and lower .014 NiTi wires after bonding. B) Upper and lower .016 x .022 NiTi wires. C) Upper and lower .017 x .025
stainless steel wires. Transpalatal arch has been placed and molar protraction
has begun. D) Completion of molar protraction.
Figure 5: Treatment Montage, occlusal-view. A) Placement of 1.6- x 6.0-mm
mini-implants with a torsional-controlled contra-angled driver. Mini-implants
placed in the para-medium region. Two mini-implants were placed to stabilize
the transpalatal arch. In critique, the mini-implants should have been placed
farther apart for greater stability. Pick-up impression taken after placement of
the mini-implants. B) We placed flowable composite to secure the transpalatal
arch to the mini-implants, and activated molar protraction with buccal and
palatal elastic chains. C) Complete consolidation in less than 5 months. Notice
the small space opening distal to the right lateral incisor, indicating a slight loss
of anchorage even with the skeletal anchorage system.
Treatment Results
The results of our treatment were an acceptable Class I relationship and a maintained facial
balance (Figure 6). We obtained an appropriate
incisal relationship by arch development, distal uprighting of the maxillary anterior teeth,
and labial advancement of the mandibular anterior teeth with mild reproximation. Evaluation of
Figure 6: Final composite photographs. Notice the second molars fully protracted into a Class I occlusion. Also notice the lingual cusp of the maxillary
left second premolar.
February 2011 OrthodonticProductsOnline.com 21
pretreatment and posttreatment cephalometric measurements showed
significant molar protraction, slight
bite opening, and minimal changes
in lip position relative to the Esthetic
Line (Figure 7).
The 6-month posttreatment records showed good retention of the
second molars and continued mesial
eruption of the maxillary third molars
into the second molar position (Figure
8, page 24).
odontogenesis. Other environmental
factors may include birth-related trauma to the teeth and jaws, trauma during intubation, poor prenatal and postnatal nutrition (specifically, vitamin A
and D deficiency), hypoxia, infections,
or exposure to toxic chemicals (such as
high dosages of fluoride, tetracycline,
and lead). Genetic factors include a
variety of hereditary conditions such
as trisomy 21, cerebral palsy, and metabolic disorders.1
Treatment options of enamel dysDiscussion
plasia depend on the severity of the le7: Superimposition. Maxillary second
Enamel Dysplasia, sometimes re- Figure
sion. Due to the nature of the dysplastic
molars and mandibular first molars were traced.
ferred to as enamel hypoplasia (EH) or
enamel, bonding is often challenging.
simply dysplasia, is a defect that results in underdeveloped Conservative treatment may consist of stainless steel crowns,
or malformed enamel. Dysplasia can occur on any tooth or composite bonding, or root canal with a full-coverage cast
on multiple teeth, though it most commonly presents on the crown. In our patient, due to the large carious lesions with
first molars or the central incisors. The enamel defect may pulpal involvement, the general practitioner recommended
present itself in a variety of forms, from a small pit-lesion extraction of the dysplastic first molars followed by protracto large orange-brownish mottling of the facial or occlusal tion of the second molars and spontaneous mesial drift of the
surface of the tooth. Teeth with enamel dysplasia are often third molars.
misshapen, hypersensitive, and may be more susceptible to
The literature demonstrates that spontaneous third
dental caries.1
molar drift following extraction of second molars is highly
The cause of dysplasia may be multifactorial, but the predicable in the maxilla (96.2%) and less predictable in the
defect is most commonly associated with infection or fe- mandible (66.2%).2 During eruption, maxillary third molar
ver during pregnancy or infancy that may interfere with crowns upright and maintain their angulation as they come
22 OrthodonticProductsOnline.com February 2011
into occlusion. Additional uprighting octreatment overbite, with or without the incurs once molar occlusion is established.2
corporation of a transpalatal arch, would
Factors that influence successful thirdhave provided sufficient dental anchorage
molar eruption include initial angle of
for molar protraction. While placement of
eruption, jaw angulation, sex, age, and
mini-implants ensured anchorage of the
developmental stage of the third molar.3
transpalatal arch, the benefit of this case
During the treatment of our patient, the
report lies in sharing a method for molar
maxillary second molars were protracted
protraction that may be more applicable
following extraction of the first molars. Figure 8: The final panorex reveals spon- when dental anchorage is insufficient.
A post-treatment panoramic radiograph taneous mesial drift of the maxillary third
revealed good erupting position and an- molars into the second molar position. The Conclusions
patient was referred for extraction of the
gulation of the maxillary third molars.
Indirect skeletal anchorage with an
mandibular third molars.
To aid efficient molar protraction,
anterior transpalatal arch can provide efwe incorporated indirect skeletal anchorage using an ante- ficient, noncompliant maxillary molar protraction. The prorior transpalatal arch. Indirect skeletal anchorage is often traction of maxillary second molars after early loss of first
preferable to direct anchorage when protracting posterior molars, and the subsequent mesial drift of the third molars,
teeth for two reasons:
allows for the reestablishment of Class I molar occlusion
1) greater biomechanical control, because forces are di- without costly posterior restorative treatment. OP
rected along a continuous archwire; and
2) greater patient safety, because the mini-implant can Neal D. Kravitz, DMD, MS, is in private practice in South
be placed in a variety of locations.
Riding, Va, and White Plains, Md. He is a Diplomate
The palate is a preferable location for indirect skeletal of the American Board of Orthodontics, and is on the
anchorage due to its dense cortical bone, attached tissue faculty at the University of Maryland and Washington
coverage, and low risk probability.4
Hospital Center. He would like to
References for this article can
With this said, mini-implants were
thank the orthodontic residents at
arguably not necessary to aid successbe found with the online version the University of Maryland for their
ful molar protraction in this particular
editorial guidance. He can be reached
at OrthodonticProductsOnline.com.
case. It is likely that the depth of preat [email protected].
24 OrthodonticProductsOnline.com February 2011